Beavers as Agents of Landscape Change

by

Cherie J. Westbrook

• LAST REVIEWED: 31 July 2019
• LAST MODIFIED: 31 July 2019
• DOI: 10.1093/obo/9780199363445-0115

Introduction

Beavers ingeniously alter environments to suit their needs of predator protection and food access, creating widespread effects on surface waters throughout their range. Beaver are thus considered the quintessential ecosystem engineer. They “engineer” landscapes largely by building dams across low-order streams to retain water. Dam building changes a wide range of ecological, hydrologic, and geomorphic processes that transform rivers into complex wetland systems capable of supporting a diversity of aquatic and terrestrial species. Although less studied, beavers live in and can significantly impact landscape processes in large rivers, wetlands, and lakes and unexpected places like landslides, brackish deltas, and glacial discharge environments. The earliest works on beaver are from a time when beaver were very much still being trapped to supply the fashion market in Europe with pelts (c. late 1800s to early 1900s). Works from this period primarily document the natural history of beaver. Research interest in beaver waned for several decades, coincident with low beaver populations. In the 1980s and 1990s, however, researcher interest in beaver was again piqued, which led to a little over a decade of studies documenting a range of ecosystem effects of beaver. Research on beaver ecosystem engineering was reinvigorated again in the mid- to late-2000s, coincident with rewilding efforts in Europe, beaver use in stream restoration activities in the United States, and rapid spread of the exotic, invasive beaver population in Tierra del Fuego. This encyclopedia entry provides a summary of the hydrogeomorphic processes known to be beaver-mediated, as well as the state of knowledge of how beaver form stream valleys and shape wetland ecosystems. Included are brief annotations of key literature. Ecological and biogeochemical impacts of beaver ponds are extensive, but a full description of them are beyond the scope of this annotated bibliography. The topic could benefit from greater synergistic and integrative research among biologists, geomorphologists, ecologists, and hydrologists.

General Overview

The works cited here are key comprehensive summaries of the effects of some aspect of beaver activities, most notably damming, on ecosystem-forming processes. Naiman, et al. 1986 is a foundational study that addresses how beaver change the structure and function of stream ecosystems. Gurnell 1998 comprehensively reviews knowledge of the physical landscape processes modified by C. canadensis and highlights limitations of the information for estimating the likely hydrogeomorphic impacts of colonization of European ecosystems by the native C. fiber. Anderson, et al. 2009 summarizes information on the destructive changes invasive beaver have made to Patagonian stream ecosystems and what the changes mean for ecosystem restoration. Parker, et al. 2012 provides understanding of niche competition between native C. fiber and invasive beaver C. canadensis in Eurasia. Westbrook, et al. 2013 is a chapter from a treatise on geomorphology that reviews general understanding and knowledge gaps of the coupled hydrologic and geomorphic processes beavers impact. Gibson and Olden 2014 reviews knowledge of beaver impacts to dryland-specific ecosystem processes. Ecke, et al. 2017 synthesizes the profound alterations beaver ponds make to the hydrochemistry of streams. Johnston 2017 comprehensively summarizes knowledge of effects of beaver impoundments on boreal ecosystems. Pollock, et al. 2017 provides an extensive review of the literature supporting the use of beaver in stream ecosystem restoration; included is reference to approximately 1,200 articles spanning the academic and grey literature. Campbell-Palmer, et al. 2016 provides an overview of the biology and ecosystem impacts of Castor fiber, with restoration and management implications in a UK context.

• Anderson, C. B., G. Martínez Pastur, M. V. Lencinas, P. K. Wallem, M. C. Moorman, and A. D. Rosemond. 2009. Do introduced North American beaver Castor canadensis engineer differently in southern South America? An overview with implications for restoration. Mammal Review 39.1: 33–52.

  Reviews the ecosystem engineering activities of beaver in North America as compared to southern South America where beaver are an exotic, invasive species. Concludes that the types and magnitude of alterations beaver make to South American ecosystems align with expectations derived from North American ecological theory.

• Campbell-Palmer, R., D. Gow, R. Campbell, et al. 2016. The Eurasian beaver handbook: Ecology and management of Castor fiber. Exeter, UK: Pelagic.

  Complication of research on the ecosystem engineering activities and biology of the Eurasian beaver. Implications of the body of research to beaver reintroduction and subsequent management in the United Kingdom is given.

• Ecke, F., O. Levanoni, J. Audet, et al. 2017. Meta-analysis of environmental effects of beaver in relation to artificial dams. Environmental Research Letters 12:113002.

  DOI: 10.1088/1748-9326/aa8979

  A meta-analysis of beaver pond effects on stream chemistry as compared to those from artificial dams. Notably, reports that beaver ponds tend to serve as a source of carbon and mercury but have little influence over nutrient (nitrogen and phosphorus) retention.

• Gibson, P. P., and J. D. Olden. 2014. Ecology, management and conservation implications of North American beaver (Castor canadensis) in dryland streams. Aquatic Conservation: Marine and Freshwater Ecosystems 24.3: 391–409.

  DOI: 10.1002/aqc.2432

  Reviews knowledge of ecological effects and management of beavers in dryland streams. Conservation implications and knowledge gaps are provided.

• Gurnell, A. M. 1998. The hydrogeomorphological effects of beaver dam-building activity. Progress in Physical Geography 22.2: 167–189.

  Thorough review of the hydrogeomorphic changes beaver make to streams, commissioned by the Scottish National Heritage during the time that it was considering reintroducing beaver. Coining of the term “geomorphic agent” to describe beaver.

• Johnston, C. A. 2017. Beavers: Boreal ecosystem engineers. Cham, Switzerland: Springer.

  DOI: 10.1007/978-3-319-61533-2

  Integration of her lifetime of scholarship on C. canadensis, primarily centered on ecosystem effects of beaver at Voyageur National Park (United States). Topics covered include soils, vegetation, and chemistry. Comparisons of insights from this boreal location are made to beaver-occupied landscapes in other parts of the world.

• Naiman, R. J., J. M. Melillo, and J. E. Hobbie. 1986. Ecosystem alteration of boreal forest streams by beaver (Castor canadensis). Ecology 67:1254–1269.

  DOI: 10.2307/1938681

  Seminal study that identifies beaver as a keystone species. Provides a broad overview of the changes beaver make to aquatic ecosystem structure and ecological dynamics.

• Parker, H., P. Nummi, G. Hartman, and F. Rosell. 2012. Invasive North American beaver Castor canadensis in Eurasia: A review of potential consequences and a strategy for eradication. Wildlife Biology 18:354–365.

  DOI: 10.2981/12-007

  Review comparing ecology and life history of the two species of beaver in Eurasia. Includes insights into niche competition and concludes with proposal of an eradication strategy for the invasive C. canadensis.

• Pollock, M. M., G. Lewallen, K. Woodruff, C. E. Jordan, and J. M. Castro, eds. 2017. The beaver restoration guidebook: Working with beaver to restore streams, wetlands, and floodplains (Version 2.0). Portland OR: US Fish and Wildlife Service.

  Guide book geared to restoration practitioners. Practical synthesis of literature for best using beaver to restore and conserve stream, floodplain, and wetland functions. Available online.

• Westbrook, C. J., D. J. Cooper, and D. R. Butler. 2013. Beaver hydrology and geomorphology. In Treatise on Geomorphology: Ecogeomorphology. Edited by D. Butler and C Hupp, 293–306. San Diego CA: Academic Press.

  DOI: 10.1016/B978-0-12-374739-6.00337-7

  Review of the influence of beaver activities on hydrologic and geomorphic processes. Emphasizes what is known and suggests future research directions.